opera hat vs silk hat

opera hat and silk hat both are nouns.

Word	Noun	Adjective	Verb	Adverb
opera hat	Yes	No	No	No
silk hat	Yes	No	No	No

As nouns, opera hat and silk hat are synonyms defined as:

opera hat and silk hat: a man's hat with a tall crown; usually covered with silk or with beaver fur

Other synonyms of opera hat include beaver, dress hat, high hat, stovepipe, top hat, topper.

opera hat (noun)	silk hat (noun)
a man's hat with a tall crown; usually covered with silk or with beaver fur	a man's hat with a tall crown; usually covered with silk or with beaver fur